(19)
(11) EP 0 462 504 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
25.03.1992 Bulletin 1992/13

(43) Date of publication A2:
27.12.1991 Bulletin 1991/52

(21) Application number: 91109665.9

(22) Date of filing: 12.06.1991
(51) International Patent Classification (IPC)5C09K 11/02, C09K 11/58, C23C 16/18, H05B 33/14
(84) Designated Contracting States:
BE DE FR GB NL

(30) Priority: 18.06.1990 US 539761

(71) Applicant: GTE PRODUCTS CORPORATION
Danvers, MA 01923 (US)

(72) Inventor:
  • Klinedinst, Keith A.
    Marlboro, MA 01752 (US)

(74) Representative: Grünecker, Kinkeldey, Stockmair & Schwanhäusser Anwaltssozietät 
Maximilianstrasse 58
80538 München
80538 München (DE)


(56) References cited: : 
   
       


    (54) Process for coating finely divided material with titania and moisture insensitive zinc sulfide luminescent materials made therefrom


    (57) A method for coating finely divided material with titania is disclosed. The method involves the fluidization of the finely divided material (16) in an inert carrier gas containing vaporized titanium isopropoxide. The isothermal fluidized bed (15) is kept at a temperature equal to or below approximately 300°C. The vaporised titanium isopropoxide reacts to form a coating of titania on the surfaces of the particles (16) within the fluidized bed (15). The greatest coating efficiency occurs when the fluidized bed is kept at approximately 300°C for approximately the first 10 minutes of the reaction and thereafter at approximated 250°C. The titania coating process is particularly useful for electroluminescent phosphors such as copper doped zinc sulfide phosphor. The titania coated electroluminescent phosphors are relatively insensitive to moisture. Lamps made from the coated electroluminescent phosphor are also relatively insensitive to moisture.







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